Calif. Meteorites May Change Life-on-Earth Theory

Van-sized space rock is a cosmic oddball

The shattered remains of a high-profile space rock are oddly low in organic materials, the raw ingredients for life. The discovery adds a slight wrinkle to the theory that early Earth was seeded with organics by meteorite impacts.

In April a van-sized meteor was seen streaking over northern California and Nevada in broad daylight. The fireball exploded with a sonic boom and sprayed the region with fragments. Videos, photographs and weather radar data allowed the meteor's trajectory to be reconstructed, and teams quickly mobilised to search for pieces in the foothills of the Sierra Nevada in northern California.

Researchers readily identified the meteorites as rare CM chondrites, thought to be one of the oldest types of rock in the universe. "Because the meteorites were discovered so freshly, for the first time we had a chance to study this type of meteorite in a pristine form," says Peter Jenniskens of the SETI Institute in Mountain View, California, who led the search effort and the subsequent study of the space rocks.

Jenniskens personally found a fragment in a parking lot, where it remained relatively free of soil contaminants. "That's the best you could hope for, other than landing in a freezer," says Daniel Glavin of NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Jenniskens and colleagues found that the California fragments also have amino acids, including some not found naturally on Earth. But in three rocks collected before a heavy rainstorm, which bathed the other pieces in earthly contaminants, organics are less abundant by a factor of 1000 than in previously studied CM chondrites.